Traveling wave tube with external helical coupler positioner



Aug. 20, 1968 DOWNEY, ET 3,398,313

TRAVELING WAVE TUBE WITH EXTERAL HELICAL COUPLER POSITIONER Filed Sept. 21. 1965 2; Ark/mew United States Patent TRAVELING WAVE TUBE WITH EXTERNAL HELICAL COUPLER POSITIONER Edward J. Downey, Jr., Warren F. Bauder, and Herman W. Cramm, Manhattan Beach, Calif., assignors to the United States of America as represented by the Secretary of the Air Force Filed Sept. 21, 1965, Ser. No. 489,088

4 Claims. (Cl. 3153.5)

ABSTRACT OF THE DISCLOSURE A traveling wave tube having a movable rod for positioning slidable helical couplers along the length of the tube while the tube is in use.

This invention relates generally to traveling wave tubes, and more particularly to a traveling wave tube structure which permits positioning and locking of coupler blocks while the tube is operating.

In the ordinary traveling wave tube an elongated section of transmission line is mounted within an evacuated envelope. The transmission line is designed as a delay line and in its basic form is a conductive helix, such as a helical metal coil. Coupled thereon is a high frequency wave which travels along the line at some relatively small fraction of the velocity of light, for example, in a tube operating at 1500 volts, which corresponds to about the speed of light, the wire in the helix Will be about thirteen times as long as the axial length of the helix, giving a wave velocity of about the speed of light along the axis of the helix or delay line.

An electron stream is projected along the helix in such a manner that the electrons in the stream and the radio frequency field produced by the helix travel in close proximity. The beam velocity is made substantially equal to, or synchronous with, the axial component of the wave velocity along the helix. While operating, a wave traveling along the transmission line interacts with the electrons in the stream to cause a redistribution in the form of partial bunching along the stream. As the wave and beam travel synchronously along the helix, the inverse phenomenon occurs, and the bunched beam induces fields and currents upon the helix. The amplitude of the wave increases along the helix because the electron stream gives up more energy than it abstracts from it. Consequently, an amplification of the radio frequency wave on the helix takes place.

It is well known in the art that modulation may be achieved through the non-linearity of a saturated electron stream of a traveling wave tube which has been bunched at one frequency by coupling onto the tube transmission line, a second wave having a different frequency. This second wave is propagated along the transmission line and interacts with the already modulated electron stream in such a manner as to produce on the main transmission line a wave which contains several frequency components including the frequency of the first wave coupled onto the transmission line as well as the sum and difference frequencies of the other waves coupled thereon. Such an arrangement is not limited to the coupling of one modulating frequency, as a plurality of such waves may be coupled into a single traveling wave tube depending on the tubes utilization.

Before this invention there was no method which permitted accurate adjustments to be made on a traveling wave tube while the tube was operating. In the case of some large rugged tubes a crude adjustment was attempted by pulling or pushing on coaxial lines, but the results of these methods proved to be far from satisfactory.

Likewise, prior to this invention, it a precise gain or 3,398,313 Patented Aug. 20, 1968 "ice phase relationship had to be achieved, the power had to be removed from the tube, and a small adjustment made on the coupler position; only then could the power be restored to the tube and a series of measurements taken to determine the effect of the coupler adjustments. This process would be repeated until the desired results were obtained. Besides consuming large quantities of time, the repeated handling of the fragile traveling wave tube increases the probability of breakage.

It is therefore an object of this invention to provide a new method and apparatus for positioning the components of electronic tubes.

It is a further object of this invention to provide a new and more efiicient apparatus for precisely locating helical couplers along the length of a traveling wave tube while the tube is operating.

It is another object of this invention to provide means for matching the gain of two or more traveling wave tubes without shutting down an entire system.

It is still another object to provide means for phase matching two or more traveling wave tubes without shutting down an entire system.

It is still a further object of this invention to provide a traveling wave tube with means for positioning and locking the coupler blocks while the tube is operating.

It is another object of this invention to provide a means for positioning components in a traveling wave tube which prevents any undue stress on the tube during assembly and disassembly operations.

It is another object of this invention to provide the means for coupling a multiplicity of signals having a precise mutual phase relationship to the helix of a traveling wave tube.

These and other advantages, features and objects of the invention will become more apparent from the following description taken in connection with the illustrative embodiments in the accompanying drawings, wherein:

FIG. 1 is a side elevation, partly in section of the traveling wave tube of this invention;

FIG. 2 is a plan view of this invention with the outer housing removed;

FIG. 3 is an end elevation view of the tube of this invention taken along line 3-3 of FIG. 1;

FIG. 4 is a cross-sectional view of the tube embodied in this invention taken along line 4-4 of FIG. 1; and

FIG. 5' is a cross-sectional view of the invention shown in FIG. 4 taken along line 5-5.

FIG. 6 is an end elevational view of a typical coupler.

Referring now to FIGS. 1 and 2, there is generally shown the traveling wave tube 10 with the outer housing 12 made of some non-magnetic or ceramic material. Mounted within the outer housing is the barrel or main carriage 14 which is supported by Teflon spacers 16 mounted at the opposite ends of the carriage.

An electron source is provided by the tube 18 which receives its power externally through the connector 20. The tube 18 has an extension 22 through which the electrons are accelerated along the main axis of the tube in conventional form. Coupler blocks 24 through 36 are adjustably mounted on the main carriage 14 and in turn surround the electron tube extension 22. The blocks are secured from relative movement by locking screws 78 as will be described hereinafter with regard to FIG. 6. Coaxial cables 38 are slidingly mounted through the end coupler 4i) and through each successive coupler until the cable reaches the particular coupler it feeds where it is attached as shown in FIG. 5. The coupler adjustment mechanism handle is shown at 54 and tube output cable at 56.

An end view of the tube showing the coaxial cables 38 coming out of the tube 10 is illustrated in FIG. 3. The locking screws 42 secure the cables and may be individually loosened to permit separate adjustment of the couplers on the main'carriage. The electron beam tube extension 46, the coupler positioning mechanism aperture 48 and the tube output cable 50 are provided for in the end coupler 40.

In FIG. 4 there is shown a section of the tube taken along the line 44 of FIG. 1 wherein the coupler 28 is slidingly mounted on the carriage 14 and held by the dovetailed slide mechanism. Included in the coupler are the coaxial cables 38a and 3812 which feed couplers 24 and 26. Aperture 48 is provided for the adjustment mechanism, while 62 is the terminus of the coaxial feed line for coupler 28; the connection to the helix surrounding the electron tube extension is at 64, While the helix terminates at the resistor 66.

Referring now to FIG. 5, illustrated is a section of the coupler taken along the line 5 of FIG. 4. The coaxial cable 38c is terminated at 62 and connected to the helix at 64 which surrounds the electron tube extension, the helix is then terminated in the coupler at the resistor 66.

Adjustment of the individual couplers is best described by referring to FIG. 1. The lock nut 74 on the coupler adjustment mechanism handle 54 is loosened, thus permitting the tube 76 to slide through the holes 48 of the coupler blocks until the end of the tube enters the coupler block to be moved. The nut 77 is then tightened which withdraws the coaxial shaft 79 slightly causing a tapered plug to expand the distal end of the tube, causing the tube to engage the coupler block; the block may then be moved by merely loosening the locking screws 42 and moving the tube assembly 76. When the desired position is reached, the lock nut 74 is tightened holding the coupler block in position while screw 42 is tightened by any conventional means including a screwdriver. The coupler positioning mechanism is then released and can be used to adjust another coupling block or can be removed from the tube entirely.

The view shown in FIGURE 6 shows the details of the locking means for the helical couplers. The main body 28 has a member 82 on each side which mates with the main body and has an extension which forms a dovetail groove which mates with the slide-on member 14 shown in FIGURE 1. The side members 80 are held to the main body by screws 78. Springs 82 provide a tension force between the head of the screw 78 and the slide member 80. In operation the screw 78 is tightened against the spring to a point where the friction between the coupler "and the slide; caused by'the 'do'v'et'ail gripping the slide; is great enough to prevent movement of the coupler except by means of a substantial force applied through the coupler positioning means.

Although the invention has been described with reference to a particular embodiment, it will be understood to those skilled in the art that the invention is capable of a variety of alternative embodiments within the spirit ,and scope of the appended claims. v

We claim: r

1. A traveling wave'tubewith adjustable. coupling means comprising: a housing; a carriage means removably mounted within the housing; a source of electrons mounted at a first end of the carriage; an electron collector mounted at a second end of the'carriage; traveling wave tube means located along the longitudinal axis of the carriage and connecting the source of electrons and the electron collector whereby electrons Will flow along said traveling wave tube means from the said'source to said collector; wave modulating means slidably mounted on the carriage and adapted to be positioned along the carriage; means for restricting the movement of the wave modulating means along the carriage means; an adjustment tube slidably mounted through one end of the housing; a shaft located within said adjustment tube adapted to expand a first end of said adjustment tube; and handle means mounted on a second end of said adjustment tube, whereby said first end of said adjustment tube will engage the wave modulating means and move it slidingly along the carriage as the handle is moved.

2. A traveling wave tube according to claim 1 wherein said wave modulating means is a helical coupler.

3. A traveling wave tube according to claim 2 wherein there are a plurality of couplers.

4. A traveling wave tube according to claim 3 wherein said plurality of couplers are relatively and independently movable.

References Cited UNITED STATES PATENTS 2,947,907 8/1960 Bodmer 315-393 X HERMAN KARL SAALBACH, Primary Examiner.

S. CHATMON, JR., Assistant Examiner. 

